IPA: /ɪnˈkʌmbənsi/
KK: /ɪnˈkʌmbənsi/
The state of holding a particular office or position, especially in government or an organization.
During his incumbency, the mayor implemented several new policies to improve the city.
Incumbency is formed from "in-" (meaning on or upon) and "cumbere" (meaning to lie down). The term refers to the state of holding a position or office, as if lying upon it.
Think of someone 'lying upon' a position ('in-' means on, and 'cumbere' means to lie down) — that's why incumbency refers to holding an office.